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Microbiology - The Unicellular Algae

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    Study Guide Microbiology – The Unicellular Algae 1. Divisions of Unicellular Algae Unicellular algae are microscopic organisms that usually exist as single cells . Because of their small size and simple structure, several groups of unicellular algae are studied in microbiology . All unicellular algae discussed here are placed in the kingdom Protista . Five major divisions are commonly considered. 1.1 Division Chlorophyta – Green Algae Members of the division Chlorophyta are known as green algae . • They contain green chlorophyll pigments • They also have carotenoid pigments • These pigments help them perform photosynthesis A well - known example is Chlamydomonas , which is widely used in laboratories and research. • Chlamydomonas produces zoospores • Zoospores are motile spores with flagella Scientists believe organisms like Chlamydomonas may be evolutionary ancestors of more complex life forms. Other members of this division include: • Volvox • Spirogyra 1.2 Division Charophyta – Stoneworts Members of the division Charophyta are commonly called stoneworts . • They grow on the bottoms of ponds • Over time, they can contribute to the formation of limestone Although they are algae, stoneworts resemble higher plants in some structural features.

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    Study Guide 1.3 Division Euglenophyta – Euglenoids The division Euglenophyta includes organisms such as Euglena . These organisms are interesting because they share features of both plants and animals : • Like plants, they contain chlorophyll and carotenoid pigments for photosynthesis • Like animals, they use flagella for movement Because of this combination of traits, euglenoids are considered an important evolutionary link . Structure and Reproduction of Euglena • A typical Euglena cell has: o A large nucleus and nucleolus o Contractile vacuoles to remove excess water o Two flagella arising from one end of the cell • Reproduction occurs by binary fission • Division takes place in the longitudinal plane 1.4 Division Chrysophyta – Golden - Brown Algae Members of the division Chrysophyta include brown and yellow - green algae . • They contain chlorophyll • They also have special carotenoid pigments called fucoxanthins • Fucoxanthins give these algae their golden - brown color A very important group in this division is the diatoms . Importance of Diatoms • Diatoms are oceanic photosynthetic algae • They form the base of many aquatic food chains • They produce large amounts of oxygen • They convert sunlight into carbohydrates , making energy available to other organisms Because of these roles, diatoms are among the most important organisms on Earth .

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